**Core Concept**
The unique control mechanism of salivary gland secretion is essential for maintaining oral health, including lubrication, digestion, and antimicrobial activity. Salivary glands are exocrine glands that produce a significant portion of the body's digestive enzymes, particularly amylase, which breaks down carbohydrates.

**Why the Correct Answer is Right**
Salivary gland secretion is primarily controlled by the autonomic nervous system, specifically the parasympathetic branch. The parasympathetic fibers release acetylcholine, which stimulates the muscarinic receptors on the salivary gland cells. This leads to an increase in the secretion of water and electrolytes, as well as enzymes like amylase. The sympathetic nervous system also influences salivary gland secretion, but its effect is more related to the composition of the saliva rather than its overall volume. The parasympathetic control is crucial for regulating the basal level of salivary secretion, which is essential for maintaining oral health.

**Why Each Wrong Option is Incorrect**
**Option A:** Hormones do not play a significant role in controlling salivary gland secretion. While certain hormones, such as adrenaline, can influence salivary gland secretion indirectly, they are not the primary regulators.
**Option C:** Chemicals like neurotransmitters do play a role in controlling salivary gland secretion, but they are not the primary controllers. The key regulators are the nerves that release these chemicals.
**Option D:** All of the above is incorrect because while hormones, chemicals, and nerves all contribute to salivary gland function, nerves are the primary controllers.

**Clinical Pearl / High-Yield Fact**
The parasympathetic nervous system's control over salivary gland secretion is essential for maintaining oral health, and its dysfunction can lead to conditions like dry mouth (xerostomia) or excessive salivation.

**✓ Correct Answer: B. Nerves**